Publications by authors named "Felix J van der Meer"

Background: The STAtins Reduce Thrombophilia trial showed that, in patients with prior venous thrombosis, rosuvastatin decreased various coagulation factor levels.

Objectives: Here, we investigated the hypothesis that statins decrease coagulation factor levels through shared mechanisms of synthesis or regulatory pathways with apolipoproteins.

Methods: We measured the levels of apolipoprotein (Apo)A-I, A-II, A-IV, (a), B-100, B-total, C-I, C-II, C-III, and E in patients (n = 126) randomized to 28 days of rosuvastatin use.

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Background: Venous thromboembolism (VTE) is a frequent cardiovascular disease with severe complications, including recurrence and death. There is a great need for alternative prophylactic treatment options as anticoagulation is accompanied by increased bleeding risk. Statins are reported to reduce the risk of incident and recurrent VTE, but the mechanisms are elusive.

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Essentials The role of statins in hemostasis and venous thromboembolism (VTE) prophylaxis is not clear. This trial assessed whether rosuvastatin use affects thrombin generation in patients with VTE. Endogenous thrombin potential and peak were decreased by 10% and 5% with rosuvastatin therapy.

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Aim: To study the effects of clinical and genetic factors on the phenprocoumon dose requirement in pediatric patients and to develop a dosing algorithm.

Methods: Pediatric patients who used phenprocoumon were invited to participate in a retrospective follow-up study. Clinical information and genotypes of genetic variations in CYP2C9, VKORC1, CYP4F2, CYP2C18 and CYP3A4 were collected and tested with linear regression for association with phenprocoumon dose requirement.

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Aims: Observational studies indicate that statins reduce the risk of recurrent venous thrombosis (VT). However, trials have not been performed and the mechanism is unknown. We aimed to determine whether statin therapy improves the coagulation profile in patients with prior VT.

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Background: Risk scores for patients who are at high risk for major bleeding complications during treatment with vitamin K antagonists (VKAs) do not perform that well. BLEEDS was initiated to search for new biomarkers that predict bleeding in these patients.

Objectives: To describe the outline and objectives of BLEEDS and to examine whether the study population is generalizable to other VKA treated populations.

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Patients receiving vitamin K-antagonists are monitored by regular assessment of the International Normalized Ratio (INR). There are two popular methods for therapeutic control of anticoagulation in patient groups: 1) Time in Therapeutic Range (TTR) assessed by linear interpolation of successive INR measurements; 2) the cross-sectional proportion (CSP) of all patients' last INRs within range. The purpose of the present study is to compare the two methods using data from 53 Dutch Thrombosis Centres and to develop a semi-quantitative model for TTR based on different types of INR change.

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Statins are said to protect against a wide range of diseases. We studied to what extent potential bias influences the results of studies on beneficial side effects of statins. We selected 8,188 atrial fibrillation patients who started treatment with anticoagulants at the Leiden Anticoagulation Clinic in the Netherlands between 2003 and 2009 and experienced 1,683 minor and 451 major bleeds during 18,105 person-years of follow-up.

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Background: After diagnosis of cancer-associated VTE, guidelines recommend considering the continuation of anticoagulant treatment until the patient is cured of cancer, although the safety of stopping anticoagulant treatment after the patient is cured has never been evaluated.

Methods: We conducted a cohort study in consecutive patients in whom cancer-associated VTE was diagnosed at the Leiden University Medical Center between January 2001 and January 2010 and monitored for the effect of cancer treatment, occurrence of recurrent VTE, major hemorrhage, and death.

Results: Of the 358 patients with cancer-associated VTE, anticoagulant treatment was continued until the death of 207 patients.

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Introduction: Introducing point-of-care (POC) INR measurement to monitor anticoagulant therapy may be beneficial for both patients and anticoagulation clinics. However, agreement between POC and laboratory INR results is still unclear, especially at sub- and supratherapeutic levels. Therefore we investigated the analytical and clinical agreement between POC INR results of the Coaguchek XS and laboratory INR results of the STA-R Evolution.

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Haemophilia A is an X-linked inherited, rare bleeding disorder, caused by a deficiency of coagulation factor VIII (FVIII). Previous studies in prophylactic dosing have demonstrated that FVIII consumption can be significantly reduced by individualising dosing based on combined analysis of individual pharmacokinetic (PK) profiling and population PK data (Bayesian analysis). So far, no studies have been performed that address perioperative concentrate consumption using iterative PK-guided dosing based on a PK population model.

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Article Synopsis
  • A study was conducted to investigate the impact of clinical dosing algorithms for acenocoumarol and phenprocoumon on the percentage of time patients spent within the therapeutic range (TTR) compared to standard care in the Netherlands.
  • The results showed that acenocoumarol users with the clinical algorithm had a significantly higher TTR and spent less time outside the therapeutic range, while phenprocoumon users did not see significant improvements in TTR.
  • The findings suggest that using a clinical dosing algorithm for acenocoumarol can enhance anticoagulation therapy quality in the first 2-12 weeks, but phenprocoumon did not show similar benefits.
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Objective: The HAS-BLED score enables a risk estimate of major bleeds in patients with atrial fibrillation on vitamin K-antagonists (VKA) treatment, but has not been validated for patients with venous thromboembolism (VTE). We analyzed whether the HAS-BLED score accurately identifies patients at high risk of major bleeds during VKA treatment for acute VTE.

Methods: Medical records of 537 patients with acute VTE (primary diagnosis pulmonary embolism in 223, deep vein thrombosis in 314) starting VKA treatment between 2006-2007 were searched for items on the HAS-BLED score and the occurrence of major bleeds during the first 180 days of follow-up.

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Patients with a second venous thromboembolism generally receive anticoagulant treatment indefinitely, although it is known that the recurrence risk diminishes over time while the risk of hemorrhage persists with continued anticoagulation and increases with age. Based on these arguments and limited evidence for indefinitely prolonged treatment, the Dutch guidelines recommend considering treatment of a limited duration (i.e.

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Background: Observational evidence suggests that the use of a genotype-guided dosing algorithm may increase the effectiveness and safety of acenocoumarol and phenprocoumon therapy.

Methods: We conducted two single-blind, randomized trials comparing a genotype-guided dosing algorithm that included clinical variables and genotyping for CYP2C9 and VKORC1 with a dosing algorithm that included only clinical variables, for the initiation of acenocoumarol or phenprocoumon treatment in patients with atrial fibrillation or venous thromboembolism. The primary outcome was the percentage of time in the target range for the international normalized ratio (INR; target range, 2.

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Background: Frozen pooled plasmas may be used for quality assessment and local calibration of prothrombin time (PT) and International Normalized Ratio (INR) measurement systems. The purpose of the present study is to estimate the long-term stability of frozen pooled plasmas stored for at least three years.

Methods: Six pooled plamas with different INR levels were stored at -70°C, -40°C, and -20°C for various time periods up to 1453days.

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Aim: To investigate whether the phenprocoumon and acenocoumarol maintenance doses are influenced by genetic variations in GATA-4, a transcription factor of CYP2C9.

Patients & Methods: The influence of seven GATA-4 SNPs on the coumarin maintenance dose was investigated by performing an analysis of variance trend analysis, stratified for CYP2C9 genotypes. Results of the best-explaining SNP were validated in the Rotterdam Study cohort.

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Background: Statins and coumarins are prescribed in combination on a regular basis. Some case reports suggested that statins might affect the dose requirements of coumarins. The aim of the study was to investigate whether acenocoumarol and phenprocoumon maintenance doses are influenced by statin use.

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Aim: To evaluate the performance of the European Pharmacogenetics of Anticoagulant Therapy (EU-PACT) acenocoumarol dose algorithms in an independent data set. The EU-PACT trial investigates the added value of pretreatment genotyping for use of warfarin, phenprocoumon and acenocoumarol.

Patients & Methods: External validation was performed in the Rotterdam Study cohort using information about 707 acenocoumarol users.

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International normalized ratio (INR) discrepancies were noted between clinical laboratories using various prothrombin time (PT) systems. We studied the influence of different commercial blood collection tubes and different PT systems on INR measurements. INRs of fresh patient samples were determined by 3 laboratories, each using different PT systems.

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Aims: Many patients treated with vitamin K-antagonists (VKA) use point-of-care (POC) whole blood coagulometers for self-testing. The majority of patients in the Netherlands use one type of POC coagulometer, that is, the CoaguChek XS. Each new lot of test strips for the CoaguChek XS is validated by a group of collaborating thrombosis centres.

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Inhibitor development is currently the most severe complication in mild/moderate haemophilia A patients, causing increased bleeding tendency, hospitalization and mortality. It has been suggested that receiving high doses of factor VIII (FVIII) concentrates for surgical procedures is an important risk factor for inhibitor development in these patients. The current multicentre study aimed to determine prospectively the incidence of inhibitor development after intensive FVIII replacement therapy for surgical procedures in patients with mild/moderate haemophilia A.

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